The present invention relates to a packing machine of the type which performs a packing operation by intermittently conveying a strip-like bag material which comprises a series of interconnected plastic bags, by filling desired goods into a leading bag section of the strip-like bag material, by heat-sealing the bag section and by separating the sealed bag section from a subsequent bag section of the bag material.
The strip-like bag material which is usually used in packing machines of the type described above has a structure as illustrated in FIG. 1. The illustrated strip-like bag material F comprises a series of interconnected bag sections B which are formed by heat-sealing a collapsed plastics film tube transversely across the same at regular intervals so as to form their respective bottoms 1 and by heat-cutting one side of the tube transversely across the same so as to form their respective opening portions 2 along and adjacent to the bottoms 1, whereby flap-like margins 3 of the welded portions 1 are formed transversely across the bag material F between the opening portions 2 and the welded portions 1, respectively. Further, the bag material F is provided, at the other side thereof, with easily severable rectilinear fragile portions 4 which are formed across the breadth of said bag material at the other side thereof at portions opposite to the opening portions 2, respectively. In the illustrated embodiment, each of the rectilinear fragile portions 4 takes the form of a row of perforations formed in the other side.
Usually, in conventional packing machines of the type described above, packing operation is performed in the following manner by the use of the strip-like bag material F. First, the bag material F is pinched between a pair of intermittently operated pinching rollers after being passed over guide rollers in such a way that its leading end depends from the pinching rollers. Then the bag material F is conveyed, by actuating the pinching rollers, for a distance corresponding to the length of one single bag so as to locate the opening portion 2 of the foremost bag section B between a pair of heat-sealers, then during inoperative interval of the drag rollers, the foremost bag B is inflated by actuating an air blower so that goods can be smoothly filled into the foremost bag B through a hopper and then after the goods have been filled therein, operation of the blower is stopped and the bag is sealed along its opening portion 2 by means of the heat-sealers and finally, the goods-charged bag is separated from the subsequent bag B of the bag material F. Thereafter, such packing operation is repeated by operating the pinching rollers.
As previously described, as the strip-like bag material F is formed with easily severable rectilinear fragile portions 4, when it is pulled by the intermittently operated drag rollers for movement, it may sometimes occur that the bag material F is caused to be broken and separated at one of the fragile portions 4 by the strain or tension imparted to it between a roll support and the drag rollers. Such accident may also occur from other causes during operation of the packing machine of the type described above.
In conventional machines of this kind, if and when such accident has happened, all of the interconnected bag sections B between the fragile portion 4 at which the bag material F has been broken and the leading end thereof become useless, since even if such accident has occurred, the drag rollers are kept operated, causing such bag sections to be discharged out of the machine, and in addition, preparation of operation of the machine, including loading of the bag material F, must be done again, which is not only troublesome, but also consumes considerable time and labor.